This invention relates to foreign particle separation and more particularly to particle separation and collection in the inlet gas flow to a turbocharger turbine.
It is well known that foreign particle injection into the inlet of a gas turbine engine can cause serious damage to the engine and its components. A turbocharged internal combustion engine relies on the exhaust gas of the engine to drive the turbine which in turn drives a compressor impeller for compression of ambient air for delivery to the engine. Historically, the turbine wheel has been made of a steel alloy in order to withstand the high temperature environment of the turbine. The design and strength of the blading has been adequate to withstand damage caused by most particles exiting the engine.
In order to reduce "turbo-lag", the weight and therefore the moment of inertia of the turbine wheel, the turbine wheels have recently begun to be made of a ceramic material. Ceramics, while capable of withstanding high operating temperatures are brittle in comparison with the alloy steel turbine wheel counterparts. Therefore, any particle in the exhaust gas poses a potential threat to the integrity of the ceramic turbine wheel.
Engine debris may come from many sources and ceramic turbine wheel failures have been caused by weld splatter shed from fabricated exhaust manifolds, oxide scale shed from both cast and fabricated exhaust manifolds, shedding of material trapped in crevices of fabricated exhaust manifolds, particles shed from cast exhaust manifolds, stainless steel protective flute particulates shed from oxygen sensors located upstream of the turbocharger, tips shed from exhaust gas thermocouples, injector tips, fragments shed from exhaust system metal gaskets, throttle plate screws injected into the engine and engine piston and exhaust valve fragments. It is therefore desirable to provide a means for separating out such particles before the exhaust gas stream comes into contact with the ceramic turbine blades. In order to preserve the integrity of the ceramic turbine wheel the separator or trap chosen must be effective in removing all unwanted particles from the exhaust gas stream. This is critical in view of the fragile nature of ceramic turbine wheel blading.
In accordance with the present invention, a turbocharger turbine housing particulate debris trap comprises a turbine housing including an inlet and outlet and a volute therebetween. A tongue extends from a point near the inlet of the turbine and separates the inlet and the volute. The tongue extends circumferentially around the turbine wheel to a point in the vertical plane tangential to the turbine wheel. The volute includes a radial expansion starting approximately below the tongue and extending downstream therefrom for approximately 90.degree. of the volute. The radial expansion of the volute leads into a passage separated from the volute by a second tongue. The passage leads into a reservoir which is separate from the volute and formed integral with the turbine housing.
Used in association with the debris trap is a system for purging the trap of collected debris. In one such system, a purge line is flow connected to the reservoir and leads to the exhaust conduit. An exhaust bypass conduit for bypassing exhaust gas around the turbine is flow connected upstream of the turbine wheel to the exhaust conduit near the inlet of the purge line. An exhaust gas wastegate valve, controlled by an actuator, opens and closes both purge line outlet and the bypass conduit, thereby expelling the collected debris from the reservoir.
Therefore, it is an objective of this invention to provide a turbocharger turbine housing particulate debris trap wherein the trap efficiency is very high for particulates large enough to cause damage to a ceramic turbine wheel.
It is another object of this invention to provide a particulate debris trap which relies on both certrifugal as well as gravitational forces to effectively trap all unwanted particulates.
It is another object of this invention to trap and collect engine debris before it impacts the turbine wheel of a turbocharger and causes damage thereto.
It is a further object of this invention to provide a system of purging the debris trap of collected foreign particles.